Classifications

• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/75—Cobalt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/005—Spinels
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/38—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals
  • B01J23/40—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of noble metals of the platinum group metals
  • B01J23/46—Ruthenium, rhodium, osmium or iridium
  • B01J23/462—Ruthenium
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/745—Iron
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  • B01J23/00—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00
  • B01J23/70—Catalysts comprising metals or metal oxides or hydroxides, not provided for in group B01J21/00 of the iron group metals or copper
  • B01J23/74—Iron group metals
  • B01J23/755—Nickel
• • B01J35/002—
• • B01J35/006—
• • B01J35/1019—
• • B01J35/1042—
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  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/30—Catalysts, in general, characterised by their form or physical properties characterised by their physical properties
  • B01J35/391—Physical properties of the active metal ingredient
  • B01J35/393—Metal or metal oxide crystallite size
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/61—Surface area
  • B01J35/615—100-500 m2/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J35/00—Catalysts, in general, characterised by their form or physical properties
  • B01J35/60—Catalysts, in general, characterised by their form or physical properties characterised by their surface properties or porosity
  • B01J35/63—Pore volume
  • B01J35/635—0.5-1.0 ml/g
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
  • B01J37/0205—Impregnation in several steps
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/02—Impregnation, coating or precipitation
  • B01J37/0201—Impregnation
  • B01J37/0207—Pretreatment of the support
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/08—Heat treatment
  • B01J37/082—Decomposition and pyrolysis
  • B01J37/088—Decomposition of a metal salt
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
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  • B01J37/00—Processes, in general, for preparing catalysts; Processes, in general, for activation of catalysts
  • B01J37/16—Reducing
  • B01J37/18—Reducing with gases containing free hydrogen
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
  • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
  • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
  • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
  • C10G2/332—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the iron-group
• • C—CHEMISTRY; METALLURGY
  • C10—PETROLEUM, GAS OR COKE INDUSTRIES; TECHNICAL GASES CONTAINING CARBON MONOXIDE; FUELS; LUBRICANTS; PEAT
  • C10G—CRACKING HYDROCARBON OILS; PRODUCTION OF LIQUID HYDROCARBON MIXTURES, e.g. BY DESTRUCTIVE HYDROGENATION, OLIGOMERISATION, POLYMERISATION; RECOVERY OF HYDROCARBON OILS FROM OIL-SHALE, OIL-SAND, OR GASES; REFINING MIXTURES MAINLY CONSISTING OF HYDROCARBONS; REFORMING OF NAPHTHA; MINERAL WAXES
  • C10G2/00—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon
  • C10G2/30—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen
  • C10G2/32—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts
  • C10G2/33—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used
  • C10G2/331—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals
  • C10G2/333—Production of liquid hydrocarbon mixtures of undefined composition from oxides of carbon from carbon monoxide with hydrogen with the use of catalysts characterised by the catalyst used containing group VIII-metals of the platinum-group
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/02—Boron or aluminium; Oxides or hydroxides thereof
  • B01J21/04—Alumina
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/06—Silicon, titanium, zirconium or hafnium; Oxides or hydroxides thereof
• • B—PERFORMING OPERATIONS; TRANSPORTING
  • B01—PHYSICAL OR CHEMICAL PROCESSES OR APPARATUS IN GENERAL
  • B01J—CHEMICAL OR PHYSICAL PROCESSES, e.g. CATALYSIS OR COLLOID CHEMISTRY; THEIR RELEVANT APPARATUS
  • B01J21/00—Catalysts comprising the elements, oxides, or hydroxides of magnesium, boron, aluminium, carbon, silicon, titanium, zirconium, or hafnium
  • B01J21/12—Silica and alumina

Definitions

• the present invention concerns the field of catalysts used for reactions for the synthesis of hydrocarbons from a gas mixture comprising carbon monoxide and hydrogen, generally referred to as Fischer-Tropsch synthesis, and more particularly a process for the preparation of a catalyst comprising an active phase comprising at least one metal from group VIII, preferably cobalt, and an oxide support, preferably silica-alumina.
• synthesis gas can be converted into hydrocarbons in the presence of a catalyst containing metals from group VIII of the periodic table of elements such as iron, ruthenium, cobalt and nickel which catalyse the transformation of a CO and H 2 mixture referred to as synthesis gas (that is to say a mixture of carbon monoxide and hydrogen), possibly diluted with carbon dioxide or any other diluent alone or in the form of a mixture such as methane, nitrogen or ethane, into hydrocarbons which are solid, liquid or gaseous at ambient temperature. That process is known by the name of Fischer-Tropsch synthesis.
• U.S. Pat. No. 6,806,226 describes by way of example cobalt-based catalysts.
• the cobalt-based Fischer-Tropsch catalysts described there suffer however from the disadvantage that they do not have a homogeneous cobalt distribution either in the catalyst grains or at the surface of the catalyst.
• the poor surface distribution of the cobalt occurs in the form of agglomeration and enrichment in cobalt at the surface and forms an external layer which is also referred to as the crust.
• the conventional procedures for preparation of catalysts used for Fischer-Tropsch synthesis generally comprise the following stages: impregnation of the support, drying, calcination and possible reduction.
• One of the ways of controlling the size, the size distribution of the crystallites and also their level of aggregation may involve optimising the drying and calcination conditions.
• U.S. Pat. No. 6,806,226 describes a catalyst obtained by vacuum impregnation and partial vacuum drying at a temperature of between 60° C. and 95° C., followed by calcination at a temperature of between 75° C. and 400° C. with a temperature ramp of between 0.5° C./min and 1° C./min for hourly space velocities (HSV) of at least 1 m 3 of air/(Kg Co(NO 3 ) 2 , 6H 2 O*h). That patent provides the possibility of much faster calcination with a temperature ramp of 100° C./min to eliminate nitrates if the HSV is higher.
• HSV hourly space velocities
• the object of the present invention is to remedy one or more of the disadvantages of the prior art by proposing a process for the preparation of a catalyst comprising an active phase comprising at least one metal from group VIII selected from cobalt, nickel, ruthenium and iron, alone or as a mixture, and an oxide support which can be used in a Fischer-Tropsch synthesis process, having an increased hydrothermal resistance as well as an activity and selectivity which is maintained in respect of C 5 + compounds in the Fischer-Tropsch synthesis process.
• a stabilisation stage comprising a drying stage which is referred to as rapid drying under specific conditions followed by a linked sequence of at least an impregnation, fluidised bed drying and calcination stage possibly in a fluidised bed made it possible both:
• Another object of the present invention is to provide a preparation process permitting the production of a catalyst which is highly active and selective in the Fischer-Tropsch synthesis process.
• a subject of the present invention concerns a process for the preparation of a catalyst comprising an active phase comprising at least one metal from group VIII selected from cobalt, nickel, ruthenium and iron, alone or as a mixture, and an oxide support, which catalyst can be used in a Fischer-Tropsch synthesis process, said process comprising:
• At least one stage for stabilisation of said oxide support consisting of:
• said stabilisation stage being followed by at least once the linked sequence of the following stages:
• An advantage of the preparation process according to the invention is that it permits the production of catalysts which are hydrothermally more stable and which have a mean size of crystallites of metal from group VIII of less than 14 nm.
• the attraction of the invention lies in the implementation, in a stage for stabilisation of said oxide support, of a specific drying stage, referred to as the rapid drying stage, which is independent of the calcination stage and carried out after the impregnation stage of said stabilisation stage.
• implementation of said drying stage in said stabilisation stage makes it possible to achieve better distribution of the metal from group VIII in the support in the initial stage for stabilisation of the support, thus facilitating the formation of the spinel phase in a strong interaction with the support by virtue of the rapid drying stage, which makes it possible to obtain enhanced hydrothermal stability for the final catalyst.
• Another subject of the present invention also concerns a process for Fischer-Tropsch synthesis from a mixture of carbon and hydrogen using a catalyst prepared according to the preparation process according to the invention, said Fischer-Tropsch synthesis process operating at a temperature of between 190 and 240° C., at a total pressure of between 1 and 5 MPa and with an H 2 /CO molar ratio of between 1.5 and 2.5.
• the process for the preparation of a catalyst comprising an active phase comprising at least one metal from group VIII selected from cobalt, nickel, ruthenium and iron, alone or as a mixture, and an oxide support, said process comprising:
• said stabilisation stage being followed by at least once the linked sequence of the following stages:
• drying is used to denote a heat treatment stage making it possible to obtain a solid with a loss on ignition (LOI) at 1000° C. of between 10 and 22% and not giving rise to the formation of crystallised cobalt oxide which can be detected by X-ray diffraction.
• LOI loss on ignition
• calcination is used to denote a heat treatment stage permitting total decomposition of the nitrates and transformation of all the counter-ions of metallic salts of the metal from group VIII (for example for cobalt, the precursor Co(NO 3 ) 2 ), to cobalt oxides.
• the catalyst prepared by the process of the invention comprises an active metallic phase comprising at least one metal from group VIII selected from cobalt, nickel, ruthenium and iron, alone or as a mixture.
• the active phase comprises cobalt.
• the active phase is advantageously deposited on an oxide support.
• the content of metal from group VIII is advantageously between 1 and 60% by weight with respect to the weight of catalyst, preferably between 5 and 30% by weight with respect to the weight of the catalyst and very preferably between 10 and 30% by weight with respect to the weight of the catalyst.
• the metallic ruthenium content is between 0.01 and 10% by weight with respect to the weight of the catalyst and very preferably between 0.05 and 0.5% by weight with respect to the weight of the catalyst.
• the active phase of the catalyst prepared according to the process of the present invention also advantageously comprises at least one additional metal selected from platinum, palladium, rhenium, ruthenium, manganese and tantalum and very preferably selected from platinum, ruthenium and rhenium.
• the additional metal or metals is or are preferably present in a content of from 0.01 to 2% by weight, preferably 0.02 to 0.3% by weight of metal with respect to the weight of the catalyst.
• the oxide support of the catalyst prepared by the process according to the invention, on which the active phase is deposited is advantageously selected from simple oxides and preferably from alumina (Al 2 O 3 ), silica (SiO 2 ), titanium oxide (TiO 2 ), ceric oxide (CeO 2 ) and zirconia (ZrO 2 ).
• That oxide support can also advantageously comprise a plurality of simple oxides selected from alumina (Al 2 O 3 ), silica (SiO 2 ), titanium oxide (TiO 2 ), ceric oxide (CeO 2 ) and zirconia (ZrO 2 ).
• the oxide support of the catalyst prepared by the process according to the invention comprises silica and alumina.
• the oxide support is formed by silica-alumina.
• the support formed by silica-alumina preferably comprises 1 to 30% by weight of silica with respect to the total weight of the support.
• the silica-alumina is homogeneous on the micrometre scale, preferably homogeneous on the nanometre scale.
• the support is in the form of a powder whose granulometry is entirely between 10 and 300 micrometres ( ⁇ m). The mean granulometry is between 50 and 120 ⁇ m.
• the preparation process comprises a stage for stabilisation of said oxide support, said stabilisation stage being implemented with the linked sequence of the impregnation, drying and calcination stages permitting deposit of the active phase.
• the stabilisation stage for the oxide support consists of:
• a drying stage referred to as the rapid drying stage, for said impregnated oxide support is carried out between the impregnation stage and the calcination stage of the stabilisation stage.
• said impregnated oxide support is entrained by means of a gas, said impregnated oxide support being subjected to a temperature rise ramp of between 250 and 600° C./min, preferably between 300 and 600° C./min, preferably between 350 and 600° C./min, more preferably between 350 and 550° C./min, the residence time of said impregnated oxide support in said drying stage being between 1 second and 1 minute, preferably between 5 and 40 seconds and preferably between 5 and 30 seconds.
• That drying stage is referred to as the rapid drying stage as the drying mode used makes it possible to achieve a very short contact time between the catalyst and the gas in a very high gas flow rate permitting the water to be very rapidly eliminated.
• the gas used in the drying stage is air, alone or mixed with an inert gas.
• the temperature of the gas at the entry to the drying stage is between 300 and 800° C., preferably between 400 and 700° C. and very preferably between 400 and 600° C.
• the pressure in the course of the drying stage is between 0.02 and 0.2 MPa and preferably between 0.05 and 0.1 MPa.
• the drying stage operates in the presence of a gas flow rate of between 2 and 4 Nl/h/g of catalyst, preferably between 2.6 and 3.2 Nl/h/g of catalyst.
• the temperature of the oxide support which is impregnated and entrained in the drying stage is between 50 and 60° C. in the preferred temperature and flow rate range.
• the drying operation is an important stage in preparation of the catalyst according to the invention.
• the impregnation, drying and calcination stages are performed independently of each other.
• the drying stage makes it possible to entrain an impregnated oxide support powder, which is possibly stabilised, being of a granulometry of less than 200 ⁇ m, and with a loss on ignition, LOI, of between 20 and 50% on issuing from the impregnation stage.
• the impregnated and dried oxide support is in the form of a powder of a granulometry of less than 200 ⁇ m and a loss on ignition measured at 1000° C. (LOI at 1000° C.) of between 10 and 22%.
• the drying stage is advantageously carried out in any apparatus known to the man skilled in the art permitting entrainment of a powder with an LOI of between 20 and 50%, of a granulometry of less than 300 ⁇ m, and making it possible to achieve a very short contact time in a very high air flow rate and at an elevated temperature.
• the drying stage is advantageously carried out in an apparatus selected from entrained beds and flash driers. Flash driers are in particular widely used in the field of agri-food and are marketed by companies like Barr-Rosin, Niro and can advantageously be used as driers in the present invention.
• the rapid drying stage which is independent of the calcination stage and carried out after said impregnation stage of said stabilisation stage makes it possible to avoid surface migration of the metal from group VIII and preferably cobalt and also avoids the formation of aggregates of the metal from group VIII and preferably cobalt within the grains of catalyst obtained.
• the rapid drying stage permits both highly efficient drying and the surprising achievement of very good distribution of the cobalt within the grains, which then facilitates the formation of a spinel phase in strong interaction with the support, thus imparting increased hydrothermal resistance to the catalyst.
• the stage for calcination of the dried and impregnated oxide support of the stabilisation stage of the process according to the invention is carried out in one or two stages.
• the calcination operation is advantageously performed in air at a temperature of between 700 and 1200° C., preferably between 850 and 1200° C. and preferably between 850 and 900° C. for a period of between 1 hour and 24 h.
• the calcination operation is advantageously performed at a temperature of between 300° C. and 600° C. in air for a period between half an hour and 3 hours, then at a temperature between 700° C. and 1200° C., preferably between 850 and 1200° C. and preferably between 850 and 900° C. for a period of between 1 hour and 24 hours and preferably between 2 hours and 5 hours.
• the oxide support on which the active phase is deposited comprises a spinel enclosed in an alumina or a silica-alumina, preferably in a silica-alumina.
• the oxide support of the catalyst is advantageously formed by a simple spinel enclosed in a silica-alumina of type MAl 2 O 4 /Al 2 O 3 .SiO 2 or a mixed spinel enclosed in a silica-alumina of type M x M′ (1-x) Al 2 O 4 /Al 2 O 3 .SiO 2 in which M and M′ are separate metals selected from the group formed by magnesium (Mg), copper (Cu), cobalt (Co), nickel (Ni), tin (Sn), zinc (Zn), lithium (Li), calcium (Ca), caesium (Cs), sodium (Na), iron (Fe) and manganese (Mn) in which Al 2 O 3 .SiO 2 denotes the chemical formula of a silica-alumina
• the stabilised oxide support obtained is formed by a spinel structure which advantageously comprises at least 5% by weight of said spinel structure, preferably at least 10% and still more preferably at least 15% by weight with respect to the total weight of the support.
• the silica-alumina in which the spinel structure is preferably enclosed preferably comprises 1 to 30% by weight of silica with respect to the total weight of the support. It is homogeneous on the micrometre scale and still more preferably homogeneous on the nanometre scale.
• the stabilisation stage makes it possible to limit the attacks of the Fischer-Tropsch synthesis reaction medium (water, acids).
• the metal from group VIII and preferably the cobalt which is added in that way involves a very strong interaction with the oxide support and cannot therefore be reduced in the Fischer-Tropsch catalyst reduction range which is well known to the man skilled in the art (reduction temperature lower than 550° C.).
• the stabilisation stage is followed by at least once the linked sequence of the impregnation, drying and calcination stages for the stabilised oxide support.
• the linked sequence of said impregnation, drying and calcination stages is performed in that order.
• the linked sequence of the impregnation, drying and calcination stages of the preparation process according to the invention is performed at least twice.
• the preparation process according to the invention therefore comprises after each impregnation stage a drying stage which is independent of the calcination stage.
• the stage for impregnation of the stabilised oxide support is advantageously performed by at least one solution containing at least one precursor of the metal from group VIII.
• stage can advantageously be effected by dry impregnation, by impregnation in excess or again by deposit-precipitation using methods well known to the man skilled in the art.
• the impregnation stage is carried out by dry impregnation, preferably at ambient temperature and preferably at a temperature equal to 20° C.
• the impregnation stage involves bringing the oxide support into contact with at least one solution containing at least one precursor of the metal from the group VIII, the volume of which is equal to the pore volume of the support to be impregnated.
• That solution contains the metallic precursors of the metal or metals from group VIII at the desired concentration to achieve on the final catalyst the desired metal content.
• the impregnation stage can also advantageously be performed at any other temperature compatible with that technology, preferably between 5° C. and 40° C., preferably between 15° C. and 25° C. and very preferably between 17° C. and 23° C.
• the first stage for impregnation of the oxide support which is possibly stabilised permits the deposit of 2 to 15% by weight and preferably 5 to 10% by weight of at least one metal from group VIII selected from cobalt, iron and ruthenium and preferably cobalt, with respect to the total mass of the final catalyst and the second stage for impregnation of the oxide support which is stabilised permits the deposit of 2 to 15% by weight and preferably 5 to 10% by weight of at least one metal from group VIII selected from cobalt, iron and ruthenium and preferably cobalt, with respect to the total mass of the final catalyst.
• the element from group VIII is cobalt
• those two stages permit the deposit of a content of metallic cobalt which can be between 4 and 30% by weight and preferably between 10 and 20% by weight with respect to the total mass of the final catalyst.
• the metal or metals from group VIII are brought into contact with the stabilised oxide support by way of any metallic precursor soluble in an aqueous or an organic phase.
• the precursor of the metal from group VIII is preferably oxalate or acetate of said metal from group VIII.
• the precursor of the metal from group VIII is introduced in aqueous solution, preferably in the form of nitrate, carbonate, acetate, chloride, oxalate, complexes formed by a polyacid or an acid-alcohol and its salts, complexes formed with acetyl acetonates, or any other inorganic derivative soluble in aqueous solution, which is brought into contact with said support.
• the cobalt precursor which is advantageously used is cobalt nitrate, cobalt oxalate or cobalt acetate.
• the stage for impregnation of the stabilised oxide support of the catalyst prepared according to the invention can also advantageously comprise at least one additional stage involving depositing at least one additional metal selected from platinum, palladium, rhenium, rhodium, ruthenium, manganese and tantalum, alone or in the form of a mixture, on said oxide support.
• the additional metal is selected from platinum, ruthenium and rhenium and very preferably the additional metal is platinum.
• Deposit of the additional metal on the support can advantageously be performed by any method known to the man skilled in the art, preferably by impregnation of the oxide support with at least one solution containing at least one precursor of the additional metal and preferably by dry impregnation or by impregnation in excess.
• the additional metal may also advantageously be added in the stage for impregnation of the metal of group VIII.
• a stage for fluidised bed drying of the impregnated and stabilised oxide support is carried out after the impregnation stage.
• the fluidised bed drying stage may be effected either in batch mode or in continuous mode, the latter mode being preferred.
• the drying stage for the impregnated stabilised oxide support is carried out in a fluidised bed, in the presence of a gas, the support being subjected to a temperature rise ramp of between 0.5 and 5° C./min, preferably between 0.7 and 4° C./min, to attain a temperature between 50 ands 170° C. and preferably between 60 and 140° C., the residence time of the support, once the drying temperature is reached, in the drying stage being between 20 and 180 min and preferably between 50 and 120 min.
• the fluidised bed technique is well known to the man skilled in the art.
• the impregnated stabilised oxide support is for example introduced after the impregnation stage on a grid, a frit or any other means making it possible to retain a solid of a granulometry of between 10 and 300 ⁇ m in the fluidised bed reactor.
• Injection of gas into the reactor under said grid at a flow rate which makes it possible to lift the powder is then effected.
• the gas flow rate is added in a manner known to the man skilled in the art to permit fluidisation.
• the gas is air, possibly mixed with an inert gas.
• a stage for calcination of the dried impregnated stabilised oxide support is carried out after the impregnation stage. That calcination stage is advantageously performed independently of the rapid drying stage.
• the calcination stage is carried out in an apparatus selected from a ventilated oven, a fluidised bed or a rotating furnace.
• the calcination step is advantageously performed at a temperature of between 320° C. and 460° C., preferably between 350 and 440° C. and preferably between 360 and 420° C. It is advantageously performed for a period of between 15 min and 15 h and preferably between 30 min and 12 h and still more preferably between 1 h and 6 h.
• the calcination stage is performed in a fluidised bed, preferably in the same apparatus as said drying stage, in the presence of a gas, the dried impregnated stabilised oxide support being subjected to a temperature rise ramp of between 0.5 and 5° C./min, preferably between 0.7 and 4° C./min, to attain a temperature of between 300 and 450° C. and preferably between 350 and 450° C., the residence time of the support, once the drying temperature attained, in said drying stage being between 5 and 120 min and preferably between 10 and 100 min.
• the catalyst obtained at the issue from the preparation process according to the invention is in oxide form after the stabilisation stage and the linked sequence of the impregnation, drying and calcination stages which is performed at least once. It has crystallites of oxide of the metal from group VIII which is present in the active phase of the catalyst, preferably crystallites of cobalt oxide CO 3 O 4 .
• the preparation process according to the invention may advantageously also comprise at least one stage for reduction of the catalyst obtained, the reduction stage being performed after the linked sequence of the impregnation, drying and calcination stages for the stabilised oxide support.
• the catalyst obtained at the end of the process according to the present invention is preferably subjected to at least one reduction stage.
• the reduction stage is intended to activate the catalyst and form particles of metal in the zero valent state and is for example performed in pure or dilute hydrogen at high temperature.
• the reduction stage is advantageously implemented at a temperature between 200 and 500° C. and for a period of between 2 and 20 hours.
• the reduction stage is advantageously effected either in situ, that is to say in the same reactor as that in which the Fischer-Tropsch reaction is performed, or ex situ before being loaded into the reactor.
• the present invention also concerns the catalyst which is capable of being produced by the preparation process according to the invention.
• the catalyst obtained at the end of the preparation process according to the invention comprises an active metallic phase comprising at least one metal from group VIII selected from cobalt, nickel, ruthenium and iron, alone or as a mixture, and an oxide support as defined hereinbefore.
• the oxide support on which the active phase is deposited may advantageously be of a morphology in the form of powder of a variable granulometry, in particular when the catalyst is used in a reactor of slurry bubble column type.
• the size of the grains of the catalyst may advantageously be between a few microns and some hundreds of microns.
• the size of the particles of the catalyst prepared using the process according to the invention is preferably between 10 microns and 500 microns, preferably between 10 microns and 300 microns, very preferably between 20 and 150 microns and still more preferably between 30 and 120 microns.
• the catalyst obtained at the end of the preparation process according to the invention has a mean size of crystallites of metal of group VIII of less than 14 nm.
• the catalyst obtained in that way comprises grains in which the metal from group VIII and preferably cobalt is distributed homogeneously in the grains and at their surface, which grains have no or little aggregates of metal from group VIII, the formation of crust at the periphery of the catalyst grains being limited.
• the distribution of the metal of group VIII and preferably cobalt in the interior of the grains of catalyst obtained by the process according to the invention and the presence or absence of a layer of metal from group VIII and preferably cobalt which is also referred to as the crust is detected for example by X-microanalysis by electronic probe or by retrodiffused-electron scanning electron microscopy (SEM).
• SEM retrodiffused-electron scanning electron microscopy
• the catalyst obtained at the end of the preparation process according to the invention may advantageously be employed in reactions carried out in suspension in a three-phase fluidised reactor, preferably of bubble column type.
• the catalyst is divided in the state of very fine powder, in particular of the order of some tens of microns and for example between 5 microns and 300 microns, preferably between 20 microns and 150 microns and still more preferably between 20 and 120 microns. That technology is also known by the terminology of the ‘slurry process’ by the man skilled in the art.
• That catalyst can also be advantageously used in different types of reactors and for example in a fixed bed, in a movable bed, in a bubble column or again in a three-phase fluidised bed.
• the invention also concerns a process for Fischer-Tropsch synthesis from a mixture of carbon and hydrogen using a catalyst prepared according to the preparation process according to the invention, the Fischer-Tropsch synthesis process operating at a temperature of between 190 and 240° C. at a total pressure of between 1 and 5 MPa and with an H 2 /CO molar ratio of between 1.5 and 2.5.
• Catalyst A1 is prepared in the following fashion:
• concentration of the solution being selected in order to attain a Co content in the silica-alumina of 5% (measured by FX) on the final stabilised support.
• the impregnated solid is then introduced into an oven swept by an uncontrolled flow of air, the temperature is raised by way of a ramp from 1° C./min to 120° C., the level is maintained for 240 min.
• the dried solid is then introduced into a high-temperature calcination furnace where it is calcined at a temperature of 850° C. minimum for at least 3 hours with a rise in the temperature with a ramp of 2.5° C./min.
• the resulting solid has a profile in respect of temperature reduction in programmed form by a 5% H2/95% argon mixture (a procedure which is well known to the man skilled in the art) with a 5° C./min ramp, which does not have any species which can be reduced prior to a temperature of 900° C. (no consumption of hydrogen by the solid).
• the reducible cobalt is then added to the support which is stabilised by dry impregnation of an aqueous solution of cobalt nitrate so as to deposit in two successive stages of the order of 14% by weight of Co.
• the solid After a first dry impregnation operation the solid is dried in a drying oven at 120° C. for 3 h in an air flow at an uncontrolled flow rate. The temperature is then raised to 420° C. using a 1° C./min ramp in an uncontrolled air flow rate for a period of 4 h.
• the intermediate catalyst contains 13.3% by weight of Co in total. It is subjected to a second dry impregnation stage by means of a solution of cobalt nitrate.
• the solid obtained is dried in a drying oven at 120° C. for 3 h in an uncontrolled flow of air. Calcination is then performed at a temperature of 420° C. using a 1° C./min ramp in an uncontrolled flow of air for a period of 4 h.
• the final catalyst A1 is obtained, which contains 19.5% by weight of Co in total.
• the mean size of the crystallites of CO 3 O 4 measured by XRD is 19 nm.
• Catalyst A2 is prepared in the following fashion:
• concentration of the solution being selected in order to attain a Co content in the silica-alumina of 5% (measured by FX) on the final stabilised support.
• the solid is then dried in an entrained bed in a flow of air with a ramp of 360° C./min in a flow of air of 2.63 Nl/h/g of catalyst for a period of 10 s in a flow of air.
• the catalyst is then discharged.
• the dried solid is then introduced into a high-temperature calcination furnace where it is calcined at a temperature of 850° C. minimum for at least 3 hours with a rise in the temperature with a ramp of 2.5° C./min.
• the resulting solid has a profile in respect of temperature reduction in programmed form by a 5% H2/95% argon mixture (a procedure which is well known to the man skilled in the art) with a 5° C./min ramp, which does not have any species which can be reduced prior to a temperature of 900° C. (no consumption of hydrogen by the solid before that temperature).
• the reducible cobalt is then added to the support which is stabilised by dry impregnation of an aqueous solution of cobalt nitrate so as to deposit in two successive stages of the order of 14% by weight of Co.
• the solid After a first dry impregnation operation the solid is dried in a fluidised bed at 90° C. in a flow of air of 1 Nl/h/g of catalyst for a period of 1 h. The dried solid is then calcined in the same fluidised bed with a 1° C./min ramp to a temperature of 400° C. in a flow of air of 1 Nl/h/g of solid and the temperature level is maintained for 1 hour.
• the intermediate catalyst contains about 13% by weight of Co in total. It is subjected to a second dry impregnation stage by means of a solution of cobalt nitrate. The solid is dried in a fluidised bed at 90° C.
• the dried solid is then calcined in the same fluidised bed using a 1° C./min ramp to a temperature of 400° C. in a flow of air of 1 Nl/h/g of solid, the temperature level being maintained for 60 min.
• the final catalyst A2 is obtained, which contains 19.5% by weight of Co in total.
• the mean size of the crystallites of CO 3 O 4 measured by XRD is 16 nm.
• Characterisation of hydrothermal resistance is implemented by bringing 2 grams of each of the catalysts studied into contact with a mixture of water, heptane, pentane (17%/48%/35% by weight respectively) at 200° C. for a period of 300 h in an autoclave using a static mode of operation under autogenous pressure.
• the catalysts A1 and A2 before being successively tested in respect of conversion of the synthesis gas are reduced ex situ in a flow of pure hydrogen at 400° C. for a period of 16 hours in a tubular reactor. Once the catalyst is reduced it is discharged in an argon atmosphere and encased in some Sasolwax® to be stored sheltered from air prior to the test.
• the Fischer-Tropsch synthesis reaction is carried out in a reactor of slurry type which functions continuously and which operates with a concentration of 10% (vol) of catalyst in the slurry phase.
• Each of the catalysts is in the form of powder of a diameter of between 40 and 150 microns.
• test conditions are as follows:
• the conversion of CO is maintained at between 45 and 50% throughout the entire duration of the test.
• test conditions are adjusted so as to be at iso conversion of CO, irrespective of the activity of the catalyst.
• the activity is 100%, the reference temperature is then equal to the base temperature.
• the catalyst A2 can therefore be considered as equivalent to the catalyst A1 in terms of intrinsic catalytic performances but the catalyst A2 is superior in terms of hydrothermal resistance.

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